Geology and Hydrocarbon Potential of Tunisia Basins

Ali Ben Ferjani, Etap Ali Chine

In Tunisia, hydrocarbon deposits have been discovered in most sedimentary rocks dating from the Paleozoic to the Tertiary. Geologically, Tunisia is subdivided in two main areas: (1) the south, with the stable Saharan platform, where Paleozoic and Triassic sandstones constitute the main petroleum objectives, and (2) the north, which includes the Tertiary and Mesozoic mobile sedimentary basins affected by tectonic movements. In the north, the stratigraphic column shows many potential reservoirs in the Tertiary and Mesozoic.

Examples of those reservoirs are found in the nummulitic limestone of the Ypresian, which produces at Ashtart and Sidi El Itayem. The Miocene sandstone is currently producing at the Tazerka field, and has proven reserves in other discoveries. The Cretaceous rocks contain many producing formations represented by the Aptian carbonate, the Barremian sandstone, the Cenomanian dolomite, and the Turonian carbonates in central Tunisia. We can find other rocks having reservoir potential equal to that of the Jurassic. These rocks have similar carbonate and sandy facies to those in the Jurassic where some discoveries were made.

The Tunisian stratigraphic column shows many levels of source rock having a geochemical potential. From the Paleozoic to the Tertiary, the main source rocks in this area are (1) Silurian shale, well-known in the entire Sahara, (2) the Albian shale and Turonian limestone, and (3) the Globigerina limestone of the Ypresian. We also can identify other levels in the Jurassic, Devonian, and Ordovician having source rock potential.

AAPG Search and Discovery Article #91032©1988 Mediterranean Basins Conference and Exhibition, Nice, France, 25-28 September 1988.